This study concerns Panic Disorder with or without Agoraphobia, conditions associated with intense discomfort and significant social incapacitation. Results from our laboratory indicate an association between agoraphobia and impaired vestibular function. Agoraphobics showed evidence for greater reliance on visual or proprioceptive cues to maintain balance. The results also indicated subclinical abnormalities on audiological test of brainstem function in anxiety disorders, but these abnormalities did not specifically occur in agoraphobia. The purpose of the proposed research is to replicate these findings and continue research begun during the previous funding period examining psychosomatic mechanisms in vestibular dysfunction. Otoneurological function will be studied in the following diagnostic groups: (1) Panic disorder (uncomplicated); (3) Panic disorder with Agoraphobia; (3) Non-panic anxiety disorder without agoraphobia-like avoidance; and (4) healthy Normal controls. Thirty subjects in each group will receive a battery of clinical audiological and vestibular tests. Normal control subjects will also undergo a test for the effect of hyperventilation on vestibular function. Physiological and self- report measures of anxiety during vestibular testing will be obtained and examined for covariation with vestibular test results. The evaluators of the audiological and vestibular tests will be blind as to the subject's diagnoses. The results of the vestibular and audiological tests will be examined with respect to prevalence of clinically abnormal findings. Parametric analysis will test for systematic differences between groups over the entire normal and abnormal range. The results of the study will have implications for our understanding of the pathogenesis of these disorders and to the development of enhanced treatments.